Method for centrifuging of tar sands froth

ABSTRACT

A method for treating tar sands bitumen froth wherein said froth is subjected to centrifugation in a first centrifuging zone to remove coarse particles therefrom and is thereafter treated in at least one second centrifuging zone to remove additional coarse particles, the overhead from the second centrifuging zone immediately downstream of the first centrifuging zone being utilized at least in part as part of the feed for the first centrifuging zone, the overhead from each succeeding second cetrifuging zone being used at least in part as part of the feed for the next prior second centrifuging zone, the overhead from the first centrifuging zone being passed to a third centrifuging zone wherein fine particles are separated thereby producing a third overhead bitumen product.

United States Patent [191 Cur'tin 111 3,811,614 [451 May21, 1974 METHOD FOR CENTRIFUGING OF TAR Primary Examiner-George H. Krizmanich PRODUCT SANDS FROTH Attorney, Agent, or FirmRoderick W. MacDonald [75] inventor: Daniel J. Curtin, Richardson, Tex. I [73] Assignee: Atlantic Richfield Company, Los [57] ABSTRACT Angeles, Calif- A method for treating tar sands bitumen froth wherein Filed: June 5 1973 said froth is subjected to centrifugation in a first centrifuging zone to remove coarse particles therefrom PP .1 6 ,199 and is thereafter treated in at least one second centriv fuging zone to remove additional coarse particles, the 52] US. Cl. 233/18 Overhead fmm the 86mm centrifuging Zone immedi' [5]] Int. Cl B04b 11/02 ately downstream of the first centrifuging me being [58] Field of Search 233/1 R, 16 17,18, 27 utilized at least in part as part of the feed for the first 233/28 centrifuging zone, the overhead from each succeeding I second cetrifuging zone being used at least in part as 56] References Cited part of the feed for the next prior second centrifuging r zone, the overhead from thefirst centrifuging zone UNITED STATES PATENTS being passed to a third centrifuging zone wherein fine 2,01 3,668 9/1935 Peltzer et al 233/16 X particles are Separated thereby producing a third over head bitumen product.

7 (Ilaims, 2 Drawing Figures 7- I 1 FIRST FIRST DECOND QZ BITUMEN F W OVERH FROTH i CENTRIFUGE V UNDER LO CENTRIFUGE FEED 2/ I zone ZONE 6 ,secono H RST *4 UNDERFLOW.

RECOVERY la THIRD I4 CENTRIFUGE ZONE h J9 TH'RD SOLlDS UNDERFLOW l2 THIRD OVERHEAD BITUMEN D'LUENT mgminIIIIIeI I974 3.811.614

FIRsT SECOND BITUMEN FIRST UNDERFLOW SECOND OVERHEAD FROTH I CENTRIFUGE I CENTRIFUGE FEED ZONE ZONE O SEOOND FIRST uNDERF Ow OVERHEAD 11/ DILUENT RECOVERY ls THIRD I4\ c NTRIFuOE 8 ZONE l ,IO'

9 TH|RD SOLIDS UNDERFLOW ---I2 THIRD OVERHEAD BITUMEN I I .F I G I PRODUCT OVERHEAD OVERHEAD 7 23 I I F l RST UN RFLOW SECOND UNDERFLOW SECOND FEED\ 7 CENTRIFUGE CENTRIFUGE CENTRIFUGE H ZONE ZONE 2 3 ZONE 2 I H/ I2 22 OvERHEAD//4 UNDERFLOW --\DILUENT I I I0 THIRD CENTRIFUGE V 2 ZONE UNDERFLOW DILUENT PRODUCT FIG. 2

BACKGROUND OF THE INVENTION This invention relates to an improvement in the plural stage centrifuging of bitumen from the froth produced in a hot water process for separating bitumen from bituminous tar sands. Tar sands are primarily composed of a fine quartz sand having a particle size greater than that passing 325 mesh screen. The quartz sand is impregnated with a viscous bitumen in quantities of from about to about 21 weight percent of the total composition. This bitumen is quite viscous and contains typically about 4.5 percent sulfur and about 38 percent aromatics. Its specific gravityat 60F. ranges typically from about 1.00 to about 1.06. In addition to the bitumen and quartz sand, the tar sands contain clay and silt in quantities of from about 1 to about 50 weight percent of the total composition. Silt is normally defined as material which will pass a 325 mesh screen but which is larger than 2 microns. Clay is material smaller than 2 microns including some siliceous material of that size.

In the hot water process for separating bitumen from tar sands, the sands are jetted with steam and mulled with a minor amount of hot water at temperatures in the range of from about 140 to about 210F. The re sulting pulp is dropped into a stream of circulating hot water and carried to a separation cell maintained at a temperature of from about 150 to about 200F. In the separation cell, sand settles to the bottom as tailings and bitumen rises to the top in the form of an oil froth. An aqueous middlings layer containing some mineral and bitumen is formed betweenthese layers. A scavenger step may be conducted on the middlings layer from the primary separation step to recover additional amounts of bitumen therefrom. These froths are then combined, diluted with naptha or other diluent and centrifuged to remove more water and residual mineral particles. The naphtha is then distilled off and the bitumen is coked toa high quality crude suitable for further processing as desired.

The bitumen product from this hot water process has a relatively specific composition. The product contains from about 35 to about 45 weight percent water and from about 5 to about weight percent mineral before dilution. The water content of this product is reduced to from about 4 to-about 6 weight percent and the mineral to from about I to about 4 weight percent before the product can be further processed. This reduction can be accomplished by plural stage centrifuging as described in Canadian Patent No. 596,561. Each stage of the centrifuging operation can consist of a single machine or each stage can comprise a battery of units connected in parallel. In these operations, the first stages are conducted by the application of relatively low forces to remove in bulk quantities the coarse mineral particle's'felg greatefih'an about 5 microns in size, while relatively higher forces are applied in the later ta sygrsmslalhsfinsminstal Pa t l s as? @299? equal to or less than 5 microns in size, and most of the water. The mineral particles and water discharged from the centrifuges must be removed from the centrifuging zone for disposal.

In this invention, reference to particle size means the diameter of the particle if it is essentially round or the 2 largest cross-sectional dimension of the particle if it is not essentially round.

Heretofore, the bitumen froth has been treated in two centrifuging zones, the first centrifuging zone removing coarse mineral particles and the second centrifuging zone removing fine mineral particles, the overhead of the second centrifuging zone being the bitumen product of that part of the tar sands froth processing plant. The underflows of the two centrifuging zones with the residual bitumen carried by both underflow streams, have been disposed of and this residual bitumen lost from the process.

SUMMARY OF THE INVENTION According to this invention, at least part of the residual bitumen heretofore lost from the froth treatment process is recovered and an increased amount of mineral particles separated from the bitumen product by employing three centrifuging zones, the first centrifuging zone being employed to remove coarse particles, the second centrifuging zone or zones operating on underflow from the first centrifuging zone or a preceding second centrifuging zone, if any, to recover additional bitumen from the minerals in the underflow from the first centrifuging zone with the overheads of these second centrifuging zones being passed at least in part to the next prior centrifuging zone as part of the feed for that next prior centrifuging zone, the overhead of the first centrifuging zone being passed to a third centrifuging zone for the separation of fine particles thereby producing a third overhead from that third centrifuging zone which is the bitumen product which contains more bitumen and less solids than the bitumen product heretofore obtained when using only two centrifuging zones.

Accordingly, it is an object of this invention to provide a new and improved method for treating tar sands froth. It is another object to provide a new and improved method for removing solids from tar sands froth. It is another object to provide'a new and improved method for increasing the recovery of bitumen from tar sands froth. It is another object to provide a new and improved method for increasing the amount of solid particles removed from a tar sands froth.

Other aspects, objects and advantages of this invention will be apparent to those skilled in the art from this disclosure and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows one embodiment within this invention.

FIG. 2 shows an alternate embodiment within this invent'ion.

DETAILED DESCRIPTION OF THE INVENTION I FIG. 1 shows a bitumen froth feed in pipe 1 passing into a first centrifuging zone 2 which is designed to remove coarse particles from the froth in a first underflow which passes into pipe 3. There is carried in this first underflow a certain amount of residual bitumen which is desirably recovered. First zone 2 can contain one or more solid-bowl or scroll-type centrifuges. There is also produced by first centrifuge zone 2 a first overhead in pipe 4 which is bitumen rich but still contains some water, some diluent if a diluent other than water is used (e.g., a hydrocarbonaceous diluent such as naphtha), and most of the fine particles that were originally in the feed in pipe 1.

The first underflow in pipe 3 passes to a second centrifuge zone 5 which contains one or more centrifuges similar to those present in first centrifuge zone 2. Second zone 5 produces a second underflow in pipe 6 which contains additional coarse particles, water, and diluent, if any. Second zone 5 also produces a second overhead in pipe 7 which is bitumen rich and is substantially reduced in coarse particle content as compared to the stream in pipe 3. The second overhead is returned at least in part as part of the feed for first zone 2 so that the bitumen recovered by way of pipe 7 is not removed from the process as was done by prior art processes but rather is returned to the process for ultimate recovery in the bitumen product. The stream in pipe 7 helps dilute the bitumen froth feed in pipe 1 thereby promoting the separation of coarse particles from the froth as well as enriching the feed for first zone 2 in bitumen.

The first overhead in pipe 4 is passed to a third centrifuge zone 8 which is designed to remove fine particles from the first overhead stream thereby producing a third overhead bitumen product in pipe 9 and a third underflow in pipe 10 which contains substantial amounts of fine particles and some residual bitumen as well as water and diluent if any is employed other than water. Zone 8 can contain one or more centrifuges such as disk-type centrifuges. The third underflow in pipe 10 can be passed in total or in part to pipe 11 and returned as part of the feed for second zone 5 for additional recovery of residual bitumen from the third underflow. This additionally recovered bitumen is ultimately passed by way of pipe 7 back to pipe 1 in the same way that additionally recovered residual bitumen associated with the coarse particles in pipe 3 is recovered and kept in the froth treatment process. The fine mineral particles which constitute the bulk of the third underflow in pipe 10 are eventually removed from the process in pipe following buildup to equilibrium concentrations in the first and second centrifuge zones 2 and 5 and subsequent separation from bitumen product into the underflow from the second centrifuging zone pipe 6. Makeup diluent can be added to pipe 11 by way of pipe 12. Of course, a special diluent can be added to pipe I if desired. Part of the material in pipe 10 can be removed from the process by way of pipe 10' if desired.

If a special diluent is employed. substantial amounts of that diluent will be in the second underflow in pipe 6 and this stream can be treated by a vaporization or other diluent recovery unit 13 to recover diluent for return to the process by way of pipe 14 and to separate the diluent from the solids in the second underflow. These solids are removed from the process altogether by way of pipe 15.

It can be seen that the bitumen froth is treated in first zone 2 for removal of some coarse particles and some water after which the first underflow therefrom is treated in at least one second zone 5 for the recovery of residual bitumen associated with those coarse particles, the residual bitumen recovered in the second overhead of zone 5 being used as part of the feed for first zone 2. It may also be seen that the fine particles are removed from the process not by the fines processing third centrifuge zone 8 (e.g., relatively smaller capacity disk-type centrifuges) but are removed in the underflow of second centrifuge zone 5 (e.g., composed of relatively higher volume scroll-type centrifuges) by entrapment, filtering and other effects exerted on the fine particles by the bulk of the coarse particles. It may also be seen that excellent clarification of the final bitumen product may be readily accomplished by reducing the percentage of the third centrifuge zone 8 feed stream in pipe 4 which is removed from the process as product in third overhead 9. This follows from the fact that clarification from solids of a centrifuge overhead product stream is most adequately performed when the underflow stream does not have to be minimized but can be a large percentage of the feed stream. The equipment configurations of FIGS. 1 and 2 allow such clarification to be accomplished to an extent greater than economically possible in the prior art case of two separate centrifuging zones in which the underflow of the fines processing centrifuge zone was discarded. This technique increases the amount of bitumen recovered by way of pipe 9 and decreases the amount of solids present in pipe 9 as compared with the prior art.

More than one second centrifuging zone can be employed to further increase the amount of residual bitumen recovered for the bitumen product and to further decrease the amount of solids present in that bitumen product. This is shown in FIG. 2 wherein, in addition to first zone 2 and second zone 5, there is employed second zone 20 which operates on the second underflow from second zone 5 and whose overhead is employed at least in part as part of the feed for the next preceding centrifuging zone, i.e., second zone 5.

In FIG. 2 the bitumen froth feed in pipe 1 is treated in first zone 2 as described hereinabove, the first underflow in pipe 3 passing to second zone 5 to be treated as described hereinabove, the second overhead from zone 5 in pipe 7 being used as part of the feed for first zone 2 as described hereinabove. However, instead of using a single second centrifuge zone as described in FIG. I, an additional second centrifuge zone 20 is employed to operate on the second underflow in pipe 21 from second zone 5. Zone 20 contains one or more centrifuges similar to the centrifuges in zone 5 and therefore operates to remove yet more residual bitumen associated with the coarse particles and, to remove additional solid particles. The additional solid particles, water, and diluent, if any, removed by way of zone 20 are taken out of the process by way of pipe 22 as waste or other disposal as desired. The additional residual bitumen recovered along with some water and diluent, if any, by zone 20 is taken as overhead in pipe 23 and used at least in part as part of the feed for the next preceding second centrifuge zone, i.e., second zone 5. At least part of the residual bitumen recovered by way of zone 20 passes through zone 5 into pipe 7, is returned as part of the feed for zone 2, finds its way into the first overhead in pipe 4, and ultimately reaches the overhead bitumen product 9. The underflow in pipe 10 can be returned by way of pipe 11 as described hereinabove as part of the feed for second zone 5, additional diluent also being supplied to pipe 11 by way of pipe 12 if desired.

Additionally, or in lieu of pipe 11, all or part of the underflow in pipe 10 can be passed by way of pipe 24 to pipe 21 as part of the feed for zone 20. Preferably, additional diluent can be employed in pipe 21 by way of pipe 25. Thus, diluent can be added at one or more of pipes l, 3, and 21 as desired while the third under flow in pipe can be added to one or both of pipes3 and 21 as desired.

More than two second centrifuge zones 5 and can be employed in this invention as desired. The overhead of each succeeding second centrifuging zone should be used as part of the feed for the next preceding centrifuge zone, each succeeding second centrifuge zone using as feed therefor the underflow from the next preceding second centrifuge zone. Thus, the hookup between zone 20 and a second centrifuge zone next succeeding zone 20 would be similar to that shown for zone 5 and its next succeeding zone 20.

EXAMPLE A bitumen froth feed containing 63 weight percent bitumen, 28 weight percent water, and 9 weight percent coarse and fine mineral particles is treated in apparatus substantially as shown in FIG. 1. The froth feed is mixed in pipe 1 with a naphtha diluent rich stream from pipe 7 and the mixture transported by way of pipe 1 into a solid-bowl centrifuge in zone 2 and there is produced therefrom a first overhead stream which is bitumen rich but contains 2 weight percent fine mineral particles, 44 weight percent water, 2l weight percent naphtha, the rest being essentially bitumen. The first underflow contains 65 weight percent coarse and fine mineral particles, weight percent water, 4 weight percent naphtha, and 6 weight percent bitumen. The first underflow is treated in second centrifuge zone 5 by a solid-bowl type centrifuge which produces a second underflow containing 65 weight percent coarse and fine mineral particles, 0.9 weight percent bitumen, 9 weight percent diluent, the remainder being essentially water, and a second overhead containing 4 weight percent residual bitumen, 4 weight percent solid particles, 48 weight percent naphtha, the rest being essentially water. Fresh naphtha is added by way of pipe 12 in the amount of 37 weight percent based on the bitumen froth feed.

The first overhead in pipe 4 is treated in third centrifuge zone 8 by a disk-type centrifuge which produces a third overhead bitumen product which contains 0.6 weight percent fine particles, 3 weight percent water, 36 weight percent naphtha, the rest being essentially bitumen and a third underflow which contains 6 weight percent fine particles, 5' weight percent residual bitumen, 3 weight percent naphtha, and the remainder essentially water. One-half of the third underflow is returned to pipe 3 wherein about half of the residual bitumen in pipe 10 is eventually recovered by way of zone 5 and finds its way into pipe 7 for return to zone 2 and ultimate recovery from zone 8 by way of pipe 9.

Reasonable variations and modifications are possible within the scope of this disclosure without departing from the spirit and scope of this invention.

The embodiments of the invention in which an exclusive property or privelege is claimed are defined as follows:

1. A method for treating tar sands bitumen froth feed containing bitumen, water, coarse mineral particles, and fine mineral particles comprising centrifuging said froth feed in a first centrifuging zone to separate a substantial amount of said coarse particles from said froth in a first underflow and leaving a bitumen rich first overhead, passing said first underflow through at least one second centrifuging zone to remove additional coarse particles, eachsuch second centrifuging zone using as part of the feed therefore the underflow of the next preceding centrifuging zone, employing at least part of the overhead of the second centrifuging zone which immediately follows said first centrifuging zone as part of the feed to said first centrifuging zone, employing at least part of the overhead of each succeeding second centrifuging zone as feed for the next preceding second centrifuging zone, centrifuging said bitumen rich first overhead in a third centrifuging zone to separate in a third underflow a substantial amount of said fine particles from said first overhead thereby providing a bitumen rich third overhead product which contains substantially less coarse and fine particles than said froth feed and employing at least part of said third underflow as part of the feed for at least one of said second centrifuges.

2. A method according to claim 1 wherein said coarse mineral particles have a size of greater than about 5 microns, and said fine mineral particles have a size of about equal to or less than 5 microns.

3. A method according to claim 1 wherein in said train of first and second centrifuging zones at least 50 weight percent of the overhead of a given zone is used as a part of the feed for the next preceding centrifuging zone.

4. A method according to claim 1 wherein a hydrocarbonaceous diluent is employed as part of the feed for at least one of said second centrifuging zones.

5.- A method according to claim 4 wherein the underflow from the last second centrifuging zone is treated for removal of diluent therefrom, and at least part of the removed diluent is reused in the centrifuging process.

6. A method according to claim 1 wherein a diluent is employed with said froth feed in said first centrifuging zone.

7. A method according to claim 6 wherein said diluent is hydrocarbonaceous. 

1. A method for treating tar sands bitumen froth feed containing bitumen, water, coarse mineral particles, and fine mineral particles comprising centrifuging said froth feed in a first centrifuging zone to separate a substantial amount of said coarse particles from said froth in a first underflow and leaving a bitumen rich first overhead, passing said first underflow through at least one second centrifuging zone to remove additional coarse particles, each such second centrifuging zone using as part of the feed therefore the underflow of the next preceding centrifuging zone, employing at least part of the overhead of the second centrifuging zone which immediately follows said first centrifuging zone as part of the feed to said first centrifuging zone, employing at least part of the overhead of each succeeding second centrifuging zone as feed for the next preceding second centrifuging zone, centrifuging said bitumen rich first overhead in a third centrifuging zone to separate in a third underflow a substantial amount of said fine particles from said first overhead thereby providing a bitumen rich third overhead product which contains substantially less coarse and fine particles than said froth feed and employing at least part of said third underflow as part of the feed for at least one of said second centrifuges.
 2. A method according to claim 1 wherein said coarse mineral particles have a size of greater than about 5 microns, and said fine mineral particles have a size of about equal to or less than 5 microns.
 3. A method according to claim 1 wherein in said train of first and second centrifuging zones at least 50 weight percent of the overhead of a given zone is used as a part of the feed for the next preceding centrifuging zone.
 4. A method according to claim 1 wherein a hydrocarbonaceous diluent is employed as part of the feed for at least one of said second centrifuging zones.
 5. A method according to claim 4 wherein the underflow from the last second centrifuging zone is treated for removal of diluent therefrom, and at least part of the removed diluent is reused in the centrifuging process.
 6. A method according to claim 1 wherein a diluent is employed with said froth feed in said first centrifuging zone.
 7. A method according to claim 6 wherein said diluent is hydrocarbonaceous. 